This invention relates to a brush assembly for a miniature electric motor, and to a method of forming the same.
The use of a graphite or graphite-based brush head mounted on a brush arm for use in an electric motor is known. Graphite segment commutators generally use this type of brush. The graphite on graphite interface significantly reduces wear and thus dust. It also generates less electrical noise.
The reduction in wear means that only a very short brush head is required allowing material savings and better space utilization within the motor. However, attachment of a shorter brush to the brush arm proves to be problematic using standard techniques due to the lack of a sizeable brush body to hold. Direct soldering is always difficult and requires a brush body with a high concentration of copper. Due to health reasons, soldering is generally avoided where possible. The common technique of using flaps on the brush arm which are resiliently deformed to grip a portion of the brush requires a significant root portion for the attachment. Hence, there is a need for a secure and reliable engagement of a brush head to a brush arm which overcomes the above mentioned problems.